Superconducting qubits can take the form of an oscillator that can transfer energy between some combination of an electric field of a capacitor, a magnetic field of an inductor, and a superconducting phase difference, such as from a Josephson junction. Phase errors can be introduced in a superconducting qubit. As one example, because the superconducting qubit can include a Josephson junction, the difference in energy between the quantum |0> and |1> states can be a function of a current in the Josephson junction that can vary to cause a fluctuation in frequency, and thus phase, in response to noise coupling into the system. As another example, when the energy of the quantum |1> state is greater than the energy of the quantum |0> state, phase always increases in time. Furthermore, timing jitter in the control pulses that are used to perform a gate operation on the superconducting qubit can translate into jitter in the phase of the superconducting qubit as the gate operation is performed.